The Cabinet approved a bill Friday to lengthen the maximum jail term for juvenile criminal offenders to 20 years from 15, allowing the government to submit it to the Diet.
The government is under pressure from people victimized by crimes to revise the Juvenile Law to narrow the gap in punishment for adults and offenders under 18 years old.
Academics and lawyers, however, have warned that the move goes against the spirit of the law, which places priority on rehabilitating young criminal offenders.
Convicted adults currently face a maximum of 30 years in prison if they are given definite terms.
"It is necessary to improve the legislation to secure public trust in the judicial system and prevent juvenile offenders from committing crimes again," Justice Minister Sadakazu Tanigaki said.
In cases where minor offenders face indeterminate sentences, the prison terms will range from 10 to 15 years from the current range of five to 10 years.